A platinum coating having high brightness has been conventionally formed on the outermost layer of an abrasion-resistant layer for improving the scratch resistance of exterior parts, personal ornaments such as glasses, accessories, and watches, decorative trims, sporting goods, and the like so as to have an appearance with a high quality feel. For example, in Patent Literature 1, an undercoat layer is formed on a base, a Ti carbide film is formed on the surface thereof by a dry coating method, and a decorative coating comprising platinum or a platinum alloy formed by a dry coating method is formed on the surface thereof. However, it has been preferable to thinly form the film since the platinum layer as the outermost layer has been expensive; and the Ti carbide film has been preferably made to have a pale color in order to suppress color change due to peeling of the thin platinum layer. Therefore, the hardness of the Ti carbide film has been low (about 40%) compared to the hardness of a typical Ti carbide film, and it has been impossible to obtain sufficient scratch resistance.
Further, when hardness is increased by increasing the amount of carbon allowed to react with the Ti carbide film in order to improve scratch resistance, a color tone is darkened although the scratch resistance is improved. Further, there is a problem that peeling of a film due to increasing film stress and pitting corrosion in a corrosion resistance test are prone to occur when the film thickness of the Ti carbide film which is a hardened layer is increased in order to similarly improve scratch resistance. Thus, it has been difficult to form the film having a film thickness of 1.0 μm or more.
Furthermore, there has been a problem that a platinum-based coating causes an allergy when the coating is brought into contact with human skin.
Thus, it has been proposed to use a Mo coating having good brightness, a good color tone, and a good low-splash property, having scratch resistance, and having a high quality feel instead of the platinum-based coating as the outermost layer. However, there has been a problem that it has been impossible to use the Mo coating without being processed since the Mo coating has had low corrosion resistance. Although it has been proposed to use a Cr coating having good brightness, a good color tone, and a good low-splash property, and having a high quality feel, there has been a problem that the Cr coating has low film hardness, resulting in insufficient scratch resistance, and it has been difficult to peel the Cr coating in a production step since the Cr coating has very high corrosion resistance.
On the other hand, it has been proposed to use, as the outermost layer, a Nb carbide film or a Ta carbide film having high hardness and having corrosion resistance. However, there has been a problem that it has been also impossible to use the coatings without being processed since the coatings have low adhesion to a base, low scratch resistance due to the impossibility of allowing a film thickness to be large, and also low brightness.